使用 telnet 测试服务器端口是否正常。

[server]$ telnet master-bb16065-2 143

如果连接，提示信息如下

Trying 172.18.0.29...
Connected to master-bb16065-2.
Escape character is '^]'.

如果想退出 telent，输入 Ctrl + ], 进入 telnet 交互接口。

telnet> help
Commands may be abbreviated.  Commands are:

close   	close current connection
logout  	forcibly logout remote user and close the connection
display 	display operating parameters
mode    	try to enter line or character mode ('mode ?' for more)
open    	connect to a site
quit    	exit telnet
send    	transmit special characters ('send ?' for more)
set     	set operating parameters ('set ?' for more)
unset   	unset operating parameters ('unset ?' for more)
status  	print status information
toggle  	toggle operating parameters ('toggle ?' for more)
slc     	change state of special charaters ('slc ?' for more)
z       	suspend telnet
!       	invoke a subshell
environ 	change environment variables ('environ ?' for more)
?       	print help information

输入 close 关闭连接。

telnet> close
Connection closed.